1. Field of the Invention
The present invention relates generally to sampling systems and, more particularly, to an automatic sampling system and method for introducing a diluted viscous sample into an instrument, such as a spectrometer, for analysis for trace elements.
2. The Prior Art
Automatic sampling systems are in widespread use today in industrial, clinical and medical laboratories. Typically, such systems include a mechanism, such as a tray, designed to hold a plurality of sample containers and present these, one by one, to a sampling station and, a further mechanism, such as a mechanical arm, designed to introduce the free end of a nozzle or tube into the sample contained within the container that has been presented at the sampling station. For most applications, samples must be diluted and mixed with an appropriate solvent. Preferably, this is done prior to the sample's introduction into the sample container. Thus, the sample solution already is properly diluted and mixed with the appropriate solvent when it arrives at the sampling station. In other instances, the instrument performing the analysis on the sample itself is provided with a suitable device to dilute and mix the sample when the same is first introduced into the instrument or shortly thereafter. Some of these devices are incorporated in the instrument or are attachments adjacent the entrance ports thereof. Further, most of these devices operate on samples or sample solutions that are for the most part non-viscous or rather low in viscosity. The demands for a sampling system operating on viscous samples, such as oils, brines, sludges and the like, are higher both in terms of aspiration, dilution and mixing than is the case for systems operating on non-viscous or lowly viscous samples. Not only is a viscous substance more difficult to aspirate, but it also is harder to dilute, harder to mix, and still harder to cleanse between sampling. These difficulties add up: to reduce sample throughput, to increase operator manipulations, thus to increase cost per sample.